The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A multiphase coupled-inductor DC-DC converter operates in continuous conduction mode (CCM) when the output power demand is high and in discontinuous conduction mode (DCM) when the output power demand is low. Most DC-DC converters that deliver high current operate in CCM, where high and low side switches of the DC-DC converter switch on and off alternately, and current in a coupled inductor of the DC-DC converter ramps up and down continuously. CCM enables the DC-DC converter to deliver high current with high efficiency.
In DCM, the DC-DC converter delivers energy to the load only when needed. When energy is needed, a high side switch turns on for certain amount of time. After the high side switch turns off, a low side switch turns on. As inductor current drops to zero, the low side switch turns-off. When energy is not needed, the switches of the DC-DC converter stop switching and remain off until energy is needed. When the switches are off, the inductor current remains zero; and an output filter capacitor supports the current when both switches are off. Accordingly, in DCM, the switching loss and the AC current related loss scale down with decreasing load current, and the DC-DC converter maintains high efficiency even at light load.